Just as chest x-rays were instrumental in finding patients who needed aggressive treatment for severe acute respiratory syndrome (SARS), they are proving important in identifying patients who could benefit from early, aggressive intervention after exposure to Asian bird flu.
Chest x-rays demonstrated more pulmonary consolidation, and in more parts of the lung, in nine patients who died as a result of infection with Asian bird flu, in a study presented at the 2005 RSNA meeting. Those findings were compared with x-ray findings in five patients who survived exposure to the disease. Among those who died, pulmonary consolidation scores exceeded 10 with at least four areas of involvement in the lungs of each patient.
Despite the small size of the study, investigators from the University of Oxford, U.K., believe that the severity of pulmonary consolidation on chest x-rays is a good predictor of survival and may single out patients who could benefit most from attentive supportive care and antiviral treatment with oseltamavir or zanamavir.
Chest x-ray results were not pathognomic for bird flu, but they did reflect an overall infectious process. Recent contact with birds and the severity of illness, as well as radiographic signs of widespread infection in the lungs, are key factors in identifying the disease.
"The x-ray features have some characteristics of viral and bacterial infections," said Nagmi Qureshi, a fellow in thoracic radiology at the University of Oxford.
The study included 98 chest x-rays obtained from 14 patients admitted to Ho Chi Minh City Hospital in Vietnam after testing positive for Asian bird flu. Vietnam is the site of the most confirmed human cases of Asian bird flu and the most human deaths resulting from the disease.
Avian influenza is now being found outside of Asia. Several young people from a rural area in eastern Turkey were diagnosed with bird flu and
subsequently died. As of late December, the World Health Organization had documented 93 cases of Asian bird flu in humans in Vietnam and 42 deaths. The WHO reports a total of 142 cases of Asian bird flu in humans and 74 deaths.
The x-rays in the study were retrospectively reviewed by independent radiologists from Vietnam and the U.K. The radiologists divided the lungs in each radiograph into three zones, a third of the craniocaudal length of the lung. Investigators then divided each lung zone into three segments and scored the degree of consolidation. Scores ranged from 0 to 18. A score of 0 was given to lung tissue that showed no signs of consolidation. A score of 18 was assessed when abnormalities were bilateral and diffuse.
The most common finding in all patients who tested positive for bird flu was multifocal consolidation. In previous studies involving patients with SARS, chest x-rays also noted multiple accumulations of infection. A 2005 study of nearly 4700 chest radiographs from 313 patients with SARS treated at the Chinese University of Hong Kong related the degree of lung opacification with survival. More than 50% of the 48 patients who died exhibited more than 20% lung opacification within seven days of symptom onset, while 86% of patients who survived demonstrated less than 10% lung opacification.
Unlike radiographs from patients with SARS, chest films from patients with Asian bird flu can depict other pathologic manifestations, including cavities in lung tissue, enlarged lymph nodes, and space surrounding the lungs, Qureshi said.
